Ad8705 Ai&r Unit 1
Ad8705 Ai&r Unit 1
Ad8705 Ai&r Unit 1
ROBOT LOCOMOTION
Introduction to AI and Robotics – robot locomotion – legged mobile robots –
wheeled mobile robots– aerial mobile robots.
Robotics is a separate entity in Artificial Intelligence that helps study the creation of
intelligent robots or machines. Robotics combines electrical engineering,mechanical engineering
and computer science & engineering as they have mechanical construction, electrical component
and programmed with programming language. Although, Robotics and Artificial Intelligence both
have different objectives andapplications, but most people treat robotics as a subset of Artificial
Intelligence (AI). Robot machines look very similar to humans, and also, they can perform like
humans, if enabled with AI.
In earlier days, robotic applications were very limited, but now they have become smarter
and more efficient by combining with Artificial Intelligence. AI has played a crucial role in the
industrial sector by replacing humans in terms of productivity and quality.
Artificial Intelligence is defined as the branch of Computer Science & Engineering, which
deals with creating intelligent machines that perform like humans. Artificial Intelligence helps to
enable machines to sense, comprehend, act and learn human like activities. There are mainly 4 types
of Artificial Intelligence: reactive machines, limited memory, theory of mind, and self-awareness.
What is a robot?
A robot is a machine that looks like a human, and is capable of performing out of box
actions and replicating certain human movements automatically by means of commands given to it
using programming. Examples: Drug Compounding Robot, Automotive Industry Robots, Order
Picking Robots, Industrial Floor Scrubbers and Sage Automation Gantry Robots, etc.
Components of Robot
Several components construct a robot, these components are as follows:
Actuators: Actuators are the devices that are responsible for moving and controlling a system or
machine. It helps to achieve physical movements by converting energy like electrical, hydraulic and
air, etc. Actuators can create linear as well as rotary motion.
Power Supply: It is an electrical device that supplies electrical power to an electrical load. The
primary function of the power supply is to convert electrical current to power the load.
Electric Motors: These are the devices that convert electrical energy into mechanical energy and
are required for the rotational motion of the machines.
Pneumatic Air Muscles: Air Muscles are soft pneumatic devices that are ideally best fitted for
robotics. They can contract and extend and operate by pressurized air filling a pneumatic bladder.
Whenever air is introduced, it can contract up to 40%.
Muscles wire: These are made up of nickel-titanium alloy called Nitinol and are very thin in shape.
It can also extend and contract when a specific amount of heat andelectric current is supplied
into it. Also, it can be formed and bent into different shapes when it is in its martensitic form. They
can contract by 5% when electrical current passes through them.
Piezo Motors and Ultrasonic Motors: Piezoelectric motors or Piezo motors are the electrical
devices that receive an electric signal and apply a directional force to an opposing ceramic plate. It
helps a robot to move in the desired direction. These are the best suited electrical motors for
industrial robots.
Sensor: They provide the ability like see, hear, touch and movement like humans. Sensors are the
devices or machines which help to detect the events or changes in the environment and send data to
the computer processor. These devices are usuallyequipped with other electronic devices. Similar
to human organs, the electrical sensor also plays a crucial role in Artificial Intelligence & robotics.
AI algorithms control robots by sensing the environment, and it provides real-time information to
computer processors.
Applications of Robotics
• Robotics in defense sectors
• Robotics in Industrial Sector
• Robotics in Entertainment
• Robots in the mining industry
Aspects of Robotics
• The robots have mechanical construction, form, or shape designed to accomplish a
particular task.
• They have electrical components which power and control the machinery.
• They contain some level of computer program that determines what, when and how arobot
does something.
Difference in Robot System and Other AI Program
Here is the difference between the two −
AI Programs Robots
There is, however, one exception: the actively powered wheel is a human
invention that achieves extremely high efficiency on flat ground. – bipedal locomotion.
Bipedal locomotion is the movement of an animal on two legs while being in anupright
position regardless of whether they are bipedal to begin with.
Our bipedal walking system can be approximated by a rolling polygon, with sides
equal in length to the span of the step.
As the step size decreases, the polygon approaches a circle or wheel. But nature did not develop a
fully rotating, actively powered joint, which is the technology necessary for wheeled locomotion.
The term degrees of freedom in robotics is widely used to define the motion capabilities of
robots, including androids (humanoid robots). In this context, the term generally refers to the
number of joints or axes of motion on the robot.
To make a legged robot mobile, each leg must have at least two degrees of freedom(DOF). For
each DOF one joint is needed, which is usually powered by one servo (a servo is a precise and powerful
way of converting rotational motion into linear motion). Because of this a four legged robot needs at
least eight servos to travel around.
Figure shows the energy consumption of different locomotion concepts. It strikes that the
power consumption of legged locomotion is nearly two orders of magnitude more inefficient than of
wheeled locomotion on hard, flat surface (e.g. railway wheel on steel). One reason for this is that
wheeled locomotion requires in general fewer motors than legged locomotion.
Power consumption of several locomotion mechanisms
When the surface becomes soft wheeled locomotion offers some inefficiency, due to increasing
rolling friction more motor power is required to move. As shown in figure, legged locomotion is more
power efficient on soft ground than wheeled locomotion, because legged locomotion consists only of
point contacts with the ground and the leg is moved through the air. This means that only a single set
of point contacts is required, so the qualityof the ground does not matter, as long as the robot is
able to handle the ground. Butexactly the single set of point contacts offers one of the most complex
problem in legged locomotion, the stability problem.
Leg configurations and stability:
Arrangement of the legs of various animals.
• Insects
–6 or more legs
• Mammals and reptiles
–4 legs
• Some mammals (Humans)
–2 legs
• Humans can jump in one leg
–complex active control to maintain balance
In general, adding degrees of freedom to a robot leg increases the Maneuverability of the
robot, both augmenting the range of terrains on which it can travel and the ability of the robot to travel
with a variety of gaits. The primary disadvantages of additional joints and actuators are, of course,
energy, control, and mass. Additional actuators require energy and control, and they also add to leg
mass, further increasing power and load requirements on existing actuators.
The major challenge in creating a single-legged robot is balance. For a robot withone leg,
static walking is not only impossible but static stability when stationary is also impossible. The robot
must actively balance itself by either changing its center of gravity or by imparting corrective forces.
Thus, the successful single-legged robot must be dynamically stable.
(ii) Two legs (biped)
Two legged robots have been shown to:
–run,
–jump,
–travel up and down stairways,
–and even do aerial tricks such as somersaults
An important feature of bipedal robots is their anthropomorphic shape. They can be built to have
the same approximate dimensions as humans, and this makes them excellent vehicles for research
in human-robot interaction.
WABIAN is a robot built at Waseda University Japan and it is designed to emulate human
motion, and is even designed to dance like a human.
WABIAN
SONY ABIBO
(iii) Four legs (quadruped)
• Standing is passively stable
• Walking is challenging because to remain stable the robot’s center of gravity mustbe actively
shifted during the gait.
Sony recently invested several million dollars to develop a four-legged robotcalled
AIBO.
To create this robot, Sony produced both a new robot operating system that is near
real-time and new geared servomotors that are of sufficiently high torque to support the robot,
yet back drivable for safety. In addition to developing custom motors and software, Sony incorporated
a color vision system that enables AIBO to chase a brightly colored ball. The robot is able to
function for at most one hour before requiring recharging.
Early sales of the robot have been very strong, with more than 60,000 units sold in the
first year. Nevertheless, the number of motors and the technology investment behind this robot dog
resulted in a very high price of approximately $1500.
Four-legged robots have the potential to serve as effective artifacts for research in
human-robot interaction.
Humans can treat the Sony robot, for example, as a pet and might develop an emotional
relationship similar to that between man and dog. Furthermore, Sony has designed AIBO’s walking
style and general behavior to emulate learning and maturation, resulting in dynamic behavior over
time that is more interesting for the owner who can track the changing behavior.
(iv) Six legs (hexapod)
Six-legged configurations have been extremely popular in mobile robotics because of their
static stability during walking, thus reducing the control complexity. In most cases, each leg has
three degrees of freedom, including hip flexion, knee flexion, and hip abduction.
.
Genghis is a commercially available hobby robot that has six legs, each of which has two
degrees of freedom provided by hobby servos. Such a robot, which consists onlyof hip flexion and
hip abduction, has less Manoeuvrability in rough terrain but performs quite well on flat ground.
Because it consists of a straightforward arrangement of servomotors and straight legs, such robots
can be readily built by a robot hobbyist.
Insects, which are arguably the most successful locomoting creatures on earth,
excel at traversing all forms of terrain with six legs, even upside down.
Currently, the gap between the capabilities of six-legged insects and artificial six- legged
robots is still quite large. Interestingly, this is not due to a lack of sufficient numbers of degrees of
freedom on the robots. Rather, insects combine a small numberof active degrees of freedom with
passives structures, such as microscopic barbs and textured pads, that increase the gripping strength
of each leg significantly.
Robotic research into such passive tip structures has only recently begun. For example, a
research group is attempting to re-create the complete mechanical function of the cockroach leg.
• (a) Standard wheel: two degrees of freedom; rotation around the (motorized) wheel
axle and the contact point.
• (b) Castor wheel or steering wheel: two degrees of freedom; rotation around an offset steering
joint. https://www.youtube.com/watch?v=LZzZbPf3xks
• (c) Swedish wheel: three degrees of freedom; rotation around the (motorized) wheelaxle, around
the rollers, and around the contact point. https://www.youtube.com/watch?v=noqBUEgyQ8A
The choice of wheel types for a mobile robot is strongly linked to the choice of wheel arrangement,
or wheel geometry. The mobile robot designer must consider these two issues simultaneously when
designing the locomoting mechanism of a wheeled robot. Why does wheel type and wheel geometry
matter?
As mentioned before the minimum number of wheels required for static stabilityis two. A
robot with a two wheeled differential drive can achieve stability if the center of mass is below the
wheel axle or if there is a third point of contact striking the floor. But these are some special cases;
under normal circumstances a wheeled robot needs at least three wheels with ground contact to
achieve static stability, additionally the center of gravity has to be completely within the support
polygon, formed by the three wheels with ground contact
(ii) manoeuvrability:
Manoeuvrability is a very important issue for a wheeled robot to solve its tasks. When a
robot is able to move in any direction of the ground plane (x,y) it is omnidirectional. This level of
movement requires usually actively powered wheels thatcan move in more than one direction like
Swedish or spherical wheels. In contrast the Ackermann steering configuration, which is used by
cars, is not omnidirectional.
Vehicles using this configuration have usually turning radius which are larger than the
vehicle itself, furthermore it is not able to move sideways (that means in axis direction), such a
movement requires several parking manoeuvres consisting of repeated changes in wheel direction
and forward and backward movement. This steering methodis very popular in hobby robotics,
because it is relatively cheap to use a remote control race car kit as a robot platform which supports
mobility
(iii) Controllability:
The advantage of omnidirectional designs is the high manoeuvrability of therobot,
but this advantage makes it more difficult to control the robot. For example, drivinga robot which
uses four powered Swedish wheels, like the Carnige Mellon Uranus robot, straight forward, all
wheels must be driven with exactly the same speed, to move in a perfectly straight line. Even little
errors in the speed of the wheels will cause mistakes in the desired travel path of the robot.
At this point the benefit of Ackermann steering appears, because controlling suchvehicles is much
easier.
Driving straight forward means just locking the steerable wheels and driving the motorized wheels.
These are connected by an axis, so the speed of the drive wheels is always the
same by actuating just one motor.
After these considerations it can be said that there is in general an inverse correlation
between controllability and manoeuvrability. If the vehicle is easy to control then it is less
manoeuvrable; if it is high manoeuvrable, controlling is more difficult.
Autonomous Capabilities:
Advanced drones are equipped with autonomous flight modes and intelligent navigation systems
that allow them to follow waypoints, orbit points of interest, and even perform complex flight paths.
Different payloads and sensors can be attached to drones, such as high-resolution cameras,
multispectral sensors, LiDAR, gas detectors, and more, depending on the application.
Aerial robots, also known as drones or unmanned aerial vehicles (UAVs), can be
categorized into two main types based on their design and flight capabilities:
Fixed-Wing Drones:
• Fixed-wing drones have a design similar to traditional airplanes, with wings that
generate lift and allow them to achieve sustained and efficient flight.
• They require a runway or hand launch for takeoff and usually land using a controlleddescent
or landing gear.
• Fixed-wing drones are well-suited for covering large distances, conducting aerialsurveys,
mapping, and performing long-duration flights.
• They tend to have longer flight times compared to multirotor drones due to them
aerodynamic efficiency.
Multirotor Drones:
• Multirotor drones, including quadcopters and hexacopters, have multiple rotors that
provide vertical lift and control.
• These drones are capable of hovering in place, making them ideal for tasks that require stable
aerial positioning, such as aerial photography, surveillance, and inspections.
• Multirotor drones are highly maneuverable and can perform intricate flight patterns, including
rotation and quick changes in direction.
• They are often used in scenarios where vertical takeoff and landing (VTOL) are essential, and
they don't require a runway.
PART - A Questions
1. Define Locomotion Mechanism.
A mobile robot needs locomotion mechanisms that enable it to move unbounded throughout its
environment. But there are a large variety of possible ways to move, andso the selection of a robot’s
approach to locomotion is an important aspect of mobile robot design. In the laboratory, there are
research robots that can walk, jump, run, slide, skate, swim, fly and of course roll.
4. What is robot?
Robots are the artificial agents acting in real world environment. Robots are aimed at
manipulating the objects by perceiving, picking, moving, modifying the physical properties of
object, destroying it, or to have an effect thereby freeing manpower from doing repetitive functions
without getting bored, distracted, or exhausted.
Q. Questions CO K Level
No. Level
1 Explain robot locomotion and its types?. CO1 K1